J.R. S. answered 04/12/20
Ph.D. University Professor with 10+ years Tutoring Experience
The neutralization reaction taking place is HCl + NaOH ==> NaCl + H2O
You will need to know the FINAL temperature of the solution which you didn't provide. I'll guide you through the process, but can't answer it without knowing the final temperature.
moles HCl = 99.8 ml x 1 L/1000 ml x 2.11 mol/L = 0.211 moles HCl (you have this right)
moles NaOH = 99.2 ml x 1 L/1000 ml x 2.05 mol/L = 0.203 moles NaOH (you have this right)
Limiting reagent is NaOH (you have this right)
Now to find the heat transfer you would use the formula q = mC∆T where m = mass of solution; C = specific heat of solution; ∆T = change in temperature of the mixture.
m = 99.8 ml + 99.2 ml = 199 ml = 199 g (assuming a density of 1g/ml)
C = 4.184 J/g/degree (assuming solution has same C as water)
∆T = final temperature - initial temperature = final temp - 24 degrees
Solve for q and that is the heat transferred (Joules) or divide by 1000 to get kJ
Enthalpy of neutralization = heat transferred (k)/0.203 moles NaOH = answer in kJ/mole